They run linux software which can enable you to share viewing cards teamed up with a motorised dish you can watch many european subscription channels via card share plus there is loads of free to air stuff to watch as well footy, films etc.
These are great! Ive got a DM500HD and cant recommend them highly enough! I set mine up using this guide on ebay and walks you through setting it up, its great gives you everything you need well worth the fiver